ENUM Administration Issues Some numbering perspectives ITU-T ENUM Workshop Geneva 17 January 2001 Tony Holmes BT tony.ar.holmes@bt.com Steve Lind AT&T sdlind@att.com

Agenda WP1/2 Liaison to IETF/ISOC Some typical call flows ENUM DNS structure and Hierarchy ENUM Considerations and issues A glossary of terms used can be found at the end of this slide pack

The Aim of this session To help raise awareness and assist administrations in understanding what needs to happen to make ENUM work To consider the administration requirements of ENUM To identify issues …..not only those that need to be tackled by the ITU but also by Member States and other parties

WP1/2 Liaison to IETF/ISOC Results of DNS Administrative discussions and Contributions - October 2000 ITU-T WP1/2 Meeting - Berlin. Understandings regarding the method for administering and maintaining the E.164-based resource data in the DNS. Administration = provision and update of E.164 numerical values, of domain “e164.arpa”, in the DNS. Example of “e164.arpa” domain name: 1.5.1.5.0.2.0.4.1.3.3.e164.arpa Administrative Zones defined: e164.arpa = Domain Zone 3.3 = Country Code Zone 1.5.1.5.0.2.0.4.1 = National Zone Note: Here ‘Zone’ refers to a segment of the domain name

WP1/2 Liaison to IETF/ISOC Agreements regarding the administration of Zones Domain Zone is outside the scope of the ITU Country Code Zone ITU provides assignment data to the DNS Administrator ITU Member States authorize/deny the ITU to notify the registrar of E164.arpa to include their Country Code No data entry for “spare” or test codes National Zone National Matter - determined by each Member State Shared Network Codes - each entity determines Groups of Countries - the administrative entity for the Group determines, in consultation with participating Member States

WP1/2 Liaison to IETF/ISOC Other Agreements Once data input is authorized, each Member State/Administrative Entity is responsible for update and accuracy of data. Data not authorized for input will not be entered in the DNS. All Administrative Entities (including the DNS Administrator) will adhere to the tenets of pertinent ITU Recommendations e.g. E.190, E.164 etc. WP1/2 will provide guidance to assist the Member States and Administrative Entities in the performance of their responsibilities - the purpose of this meeting.

Typical call flows PSTN - IP Gateway IP Network DNS +44 1473 123456 +41 22 730 5887 DNS look up returns NAPTR record with itu@sipservice.foo 4 6 DNS returns SIP server IP address 5 Gateway looks up host for itu@sipservice.foo 7 SIP server routes call to user +41 22 730 5887 1 +41 22 730 5887 2 ( ENUM functionality) formats url 7.8.8.5.0.3.7.2.2.1.4.e164.arpa 3

Typical call flows IP - PSTN 3 DNS returns record as url tel:+441473123456 +44 1473 123456 +41 22 730 5887 PSTN Gateway IP Network DNS Location server 1 +44 1473 123456 2 Client formats url 4 SIP Client initiates INVITE to server using tel url 6 LS returns IP address of Gateway 5 SIP sever looks up gateway address from LS 7 Call routed to Gateway IP address 8 Gateway completes call to PSTN

ENUM - DNS Structure & Hierarchy e164.arpa RIPE NCC Tier 1 Registry 4.4.e164.arpa Tier 2 Service Registrar 1.6.e164.arpa Tier 3 Application Service Provider

ENUM Considerations - 1 Inserting numbers in the DNS Tier 1 Registry Registries will be identified by each participating Member State Entries will point to the Service Registrar for a number ITU & IETF position states: ITU has responsibility to provide assignment information. Geographic Country Codes will only be included in the DNS when authorised by the Member State responsible for that code ISSUE An agreed process needs to be developed e.g. between appropriate authorities (participating Member States, potentially ITU-T) and Tier 1 Registries

ENUM Considerations - 2 Inserting numbers in the DNS Tier 1 Registry ITU & IETF position states: Each administration is responsible for ensuring DNS administrators (Registries) are aware of appropriate changes ISSUES Maintaining integrity of E.164 Building ENUM integrity Not all countries have the same regulation or rules of administration BUT all need to address the same issues for ENUM How should Tier 1 Registries be selected? - it’s a national matter but there are options…….

ENUM Considerations - 3 Inserting numbers in the DNS Tier 1 Registry …could be one or more Tier 1 Registry providers per CC e.g. - integrated number plan could be separated by national authorities - Tier1 Registry(s) could be separated by number ranges within a CC but there can only be one Registry per E.164 number ISSUES How to determine the most appropriate arrangement? Who runs national Registries? An agreed process needs to be developed between participating Member States and their Tier 1 Registry provider(s) (national matter).

ENUM Considerations - 4 Inserting numbers in the DNS Tier 1 Registry ITU & IETF position states: For national zone resources behind the CC shared by Networks the resource assignee is responsible for providing E.164 assignment information to the DNS Administrator Network Code assignees need to be made aware of ENUM rules ITU Recs may require amendment to embrace this ITU & IETF position states: For national zone resources behind the CC shared by Groups of Countries the resource assignee is responsible for providing E.164 assignment information to the DNS Administrator ITU Recs may require amendment/development to embrace this

ENUM Considerations - 5 Inserting numbers in the DNS Tier 1 Registry Entries in the Tier 1 Registry point to the Service Registrar for an E164 number e164.arpa Tier 2 Service Registrar ISSUE In some cases with Number Portability, the name server must point to a Service Registrar on an individual E164 number basis, not a number block The full implications on all methods of NP and associated processes need to be understood

ENUM considerations - 6 Inserting numbers in the DNS Enables the use of an E.164 number allocated to a Service Provider to be used to deliver calls to another Service Provider ISSUES Network by-pass Some countries are moving to single number administration and payment for numbers, does this raise additional issues? Rights of ownership? - differences across administrations? - Intellectual Property Rights?

ENUM considerations - 7 Inserting numbers in the DNS Enables the use of an E.164 number allocated to a Service Provider to be used to deliver calls to another Service Provider ISSUES Customer perception where an E.164 number that provides access to an ISP, other than the one responsible for the number, experiences differing QoS and cost? Privacy of information/consumer protection Legal intercept? Regulatory implications e.g monitoring of QoS etc?

ENUM Considerations - 8 Inserting numbers in the DNS Tier 2 Service Registrar e164.arpa Tier 1 Registry Tier 2 Service Registrar hosts NAPTR records for E.164 numbers All records for a given number must be in one name server points to Registry points to Service Registrar for an E.164 number ISSUE Determination of who qualifies to be a Service Registrar? Two alternatives under discussion Model 1 - any accredited domain name/service registrar Model 2 - telephone service provider

Reference Model I (General) Legend ASP Application Service Provider T1E Tier 1 Entity (Registry) T2E Tier 2 Entity (Registrar) TSP Telephony Service Provider EU End User T1E New T2E A H ** End User can be the end user itself or an agent authorized to represent the end user. ** TSP can offer application services also. The “TSP” entity performs functions specific to the TSP. B C T2E E U F G E D TSP ASP

ENUM Considerations - 9 Model I Pros & Cons Pros: Reference Model I T1E New T2E Model I Pros & Cons A H C T2E E U B G F E D TSP ASP Pros: EU determines T2E, EU has more control EU can be T2E (e.g., universities and enterprises) for his/her own E.164 number(s) Enable competitive T2E service offering Cons: More complicated interactions among involved entities More efforts at T2E to manage the NAPTR RRs

Reference Model II (T2E=TSP) Legend ASP Application Service Provider T1E Tier 1 Entity T2E Tier 2 Entity TSP Telephony Service Provider EU End User A’ B’ T2E/TSP E U ** End User can be the end user itself or an agent authorized to represent the end user. ** TSP can offer application services also. The “TSP” entity performs functions specific to the TSP. E’ C’ D’ New T2E/TSP ASP

ENUM Considerations - 10 Pros: Fewer interfaces to deal with Reference Model II Pros: Fewer interfaces to deal with Easier to verify End Users’s identity and ownership of the E.164 Number More incentives for TSPs to get involved in ENUM process (e.g., verify End User’s ownership of a E.164 Number and inform T1E about E.164 number service disconnect) T1E B’ A’ T2E/TSP E U E’ C’ D’ New T2E/TSP ASP Cons: Only TSPs can be T2E, non-competitive if there is only one TSP in a serving market Non-TSPs cannot be T2E End Users cannot be T2E for their own E.164 Numbers End Users cannot get ENUM service if none of TSPs in the serving market offers ENUM service

ENUM Considerations - 11 Inserting numbers in the DNS Tier 2 Service Registrar Some Administration issues from the Service Registrar models Is one, or a number of different model(s) preferable? Who should be Service Registrars? How can E.164/DNS integrity be safeguarded if responsibility for number insertion in the DNS lies with the customer? How should validation of subscriber identity, data & NAPTR (service records) occur? How can number/name hijacking/fraud be prevented?

ENUM Considerations - 12 Inserting numbers in the DNS ISSUES How will number changes/number churn be handled? How will ceased numbers be notified/recovered? Could prepaid mobile numbers be inserted? If so how will ownership be validated ? How will changes/ownership/loss/ theft/cease issues be addressed? Who has these responsibilities?

ENUM Considerations - 13 Inserting numbers in the DNS ISSUES Geographic numbers would lose location information, will begin to look more like personal numbers Impact on number plans/number administration? Are additional controls required where numbers are shared? Should/could requirements on carriers/third parties be enforced? Do ENUM procedures and rules apply if E.164 numbers are inserted in other domain name space (e.g .com/other domains) ?